First of all that assertion is crap. Matter of fact I pointed out to one of your equally upset Croat brethren that Servium was a city in the Balkans many years before any Slavs were registered suggesting a more ancient European presence for the Serbs (and frankly Croats probably too) – perhaps tied to the Jazyges. Second, keep conspiracy theories – whether regarding the “Vatican” or Azeri Albanians or whatever – out of this.
As mentioned in Chronicles language is Serbian for all Slavs. And it, indeed started from Balkans, from Vinča civilization centered around present day Belgrade.
This was a cradle of European civilization from more than 7000 years ago. Language was proto-Slavic or Serbian that was with migration spread through Russian steppes all the way to India where it was known as Sanskrit.
BTW Dalimil Chronicle starts with chapter
1. Babylonian Tower, Serbian (Babilonska Viež, Srbove) – Story about how Serbs have built a tower in Babylon aiming to reach for heaven and were punished by God to be dispersed and for Serbian language that was universal at the time to be changed into many languages including Greek and Roman/Latin.